Technical - How to calculate the material requirement for cement mortar

The main problem in the calculation of the quantity of cement and sand in mortar / render / screed / plaster is that we have remember so many numerical values? 

All mix ratio engineer must remember? 

For plastering? 

For BBM? 

For screed? 

Is there any easy method to do the calculation? Is this rule will be as per construction standard? No, not required.....

Take a look or the below video:

What is frog in brick?

In the 1930's the bricks were made by hand in slop moulds and the indent required a wooden former in the bottom of the mould box. This looked like a crouching frog and the name stuck despite its reference to the indent. Some manufactures make the impression of company symbol or there short name also.

Frogs less than 3/8 inch deep don't affect the net area of the unit. Some experts say that bricks containing frogs should be laid with the frog up so that the frog is completely filled with mortar. If the brick is laid with the frog on the bottom, the frog may not get completely filled with mortar.

Many thanks to google.com and doc88.com, from where the details were collected.